A clear-coated stainless steel sheet has frequently been used for chassis of home appliances, interior furnishing materials, and external materials because a luxury appearance can be obtained using the characteristic aesthetically pleasing metallic gloss of a stainless steel. However, since the clear-coated stainless steel sheet has a feature of an extremely high gloss, there is a problem in that pressure printings caused by pressures during coiling of the steel sheet or scratches on the coated surface are easily noticed.
With regard to a clear-coated stainless steel sheet with excellent scratch resistance and excellent workability, a method of manufacturing a clear-coated stainless steel sheet with enhanced workability and enhanced scratch resistance is disclosed which includes a primer coating process and a top coating process (for example, Patent Document 1). In the primer coating process, a coating film having a low elastic modulus and a thick film thickness is formed by a two coat and two bake system (coating two times and drying two times). In the top coating process, a coating film having a high elastic modulus and a thin film thickness is formed. However, it is necessary to include the coating process of two coat and two bake, and it is necessary to differentiate coating materials of the primer coat and coating materials of the top coat and to control the respective film thicknesses as well. Therefore, extremely complicated coating management is required, which is unrealistic in consideration of the workability.
In addition, it has been reported that, with regard to a method of coating both of the front and rear surfaces of a base material, anti-pressure printing property is improved by adding resin particles to a rear surface coating portion (Patent Document 2). Generally, in the case of a coated steel sheet in which an ordinary steel is used, it is common to coat the rear surface in order to suppress the occurrence of rusts. However, there are cases in which coating on the rear surface is restricted depending on products in which the manufactured coated steel sheet is used. In addition, since it is necessary to carry out special coating for the rear surface, this results in an additional increase in the costs.
Furthermore, it has been reported that, when a pre-coated steel sheet is manufactured by a two coat and two bake system, the anti-pressure printing property is improved by adding resin beads to the top coat, and the particle diameter of the resin beads is defined (Patent Document 3). However, since the film thickness of the coated film is thick, and the particle diameter of the beads is large in the pre-coated steel sheet, it is difficult to apply the method to stainless clear coating from the viewpoint of designability.
Meanwhile, as the related art in which the amount of the resin beads is defined, a technique is reported that improves the designability of a clear-coated stainless steel sheet by a one coat and one bake process (Patent Document 4). However, the anti-pressure printing property during manufacturing is not described.
So far, a clear-coated stainless steel sheet has not been developed yet in which anti-pressure printing property, scratch resistance, and workability are balanced, and which can be manufactured by a once coating and once baking method with excellent workability such that baking can be conducted within a short time.